I think the perfect surface for fully bare foot running would be a golfing green, or perhaps a beach with great sand.
Now there is a huge difference between running with shoes on and running in 5-finger shoes. First of all, we've been trained to wear shoes most of our lives. We are not used to walking or running barefoot for long periods of time. Naturally we are going to toe or mid-foot strike when we are barefoot, but with shoes, we learn to heel strike. This is important.
When you start wearing barefoot shoes, you're foot is in for a rude awakening. All those muscles that have just been hanging out, relaxing in your shoes, are now going to have to work. For this reason, if you decide you need to be at one with nature, and go barefoot running, make sure you ease your way into it. Otherwise, you will have some pretty bad foot pain, possible over-use injuries, and no fun.
When you go to REI or wherever you may find these 5 finger shoes, be sure to ask the salesman what 5-Finger or Vibram recommends for breaking them in. So far, I've heard the best way is to only wear them 30 minutes at a time, slowly ease your way into an hour, and keep doubling the time over several weeks. Do not attempt running in your 5 finger shoes until you have mastered walking around in them on a daily basis.
If you choose to continue running in your shoes, make sure you have good shoes. I cannot tell you how many people I have trained who have injuries that could have been avoided if they'd been wearing better shoes. Go somewhere and get a gait analysis, make sure you are put in the proper footwear for your particular gait. If you have knee pain, or shin splints, you are probably in the wrong shoes. I know it's expensive, but it is worth the money you are going to save on surgery down the road.
(Don't worry.. you don't actually have to do a gait analysis in your underwear)
If you have any questions or want advice on this topic, please feel free to email me at email@example.com.